This invention relates to electric motors and in particular, to a blower motor for use in a bypass or wet-type vacuum cleaner application.
Blower motors in bypass vacuum cleaners have an impeller which moves air from an inlet to an outlet of an impeller housing fitted to the motor without passing through the motor itself. This construction allows the vacuum cleaner to suck up liquids as well as dust and dirt without damaging the electric motor.
The impeller is mounted on a shaft of the motor. The shaft is journalled in a bearing where it passes through an end bracket of the motor housing which also acts as a divider between the motor and the impeller. Unfortunately, the impeller, while moving air through the impeller housing, creates a large air pressure differential across this bearing. This pressure differential can result in leakage of air through the bearing and into the motor housing proper. This has many potential dangers. Moisture laden air may seep into the motor causing electrical short circuits and/or rusting of motor parts. Entrained dust can contaminate the bearings resulting in rapid failure and even if the air is clean, the leakage removes oil and grease from the bearing leading to a dry bearing and premature bearing failure. The use of sealed bearings is not sufficient and the use of secondary oil seals is common. However, the oil seals require lubrication in the form of grease to reduce the wear on the oil seal lips where they contact the shaft. This is especially important for the modern high speed blower motor assemblies. The lips of the oil seal are relatively rigid to withstand the high air pressure differential across the oil seal. This rigidity comes from making the lips thicker and shorter which reduces the available space between the lips for the lubricating grease. Once the grease has been used up, the oil seal quickly wears out, leading to motor failure.
The present invention seeks to overcome this problem by creating a larger grease reservoir between the shaft and the lips of the oil seal. This is achieved by providing a groove in the shaft between the lips of the oil seal.
Accordingly, the present invention provides an electric motor having a rotor including a shaft, a stator, bearings associated with the stator supporting the shaft, and an oil seal associated with one of the bearings, said oil seal contacting the shaft at two axially spaced locations and forming a cavity for lubricating grease, wherein the shaft has a groove located between said spaced locations to increase the volume of the cavity.
Preferred and/or optional features are set forth in the dependent claims.